function orbitalPeriod(arr) {
    const GM = 398600.4418;
    let earthRadius = 6367.4447;

    arr.forEach(item => {
        item.orbitalPeriod = Math.round(
            Math.PI * Math.sqrt(Math.pow(earthRadius + item.avgAlt, 3) / GM) * 2
        );
        Reflect.deleteProperty(item, "avgAlt");
    });
    return arr;
}

// test here
orbitalPeriod([{ name: "sputnik", avgAlt: 35873.5553 }]);
